In recent years, there were several incidents in which a suspicious person intruded into, for example, a classroom while students were in class and killed the students and teachers. Various measures are taken against such a crime. Conventionally, there is known an alarm apparatus that outputs an alarm for informing a security center or the like of, for example, intrusion of a suspicious person.
Patent Literature 1 discloses an alarm apparatus that can identify a location where an incident occurs and take quick and appropriate measures. In the alarm apparatus described in Patent Literature 1, alarm switches are provided in classrooms and, when the alarm switch is operated, an emergency signal is transmitted to a broadcasting room. In the broadcasting room, a classroom is identified on the basis of the emergency signal. An alarm lamp corresponding to the identified classroom is turned on. Accordingly, it is possible to quickly locate a classroom in which an incident occurs.